As shown in FIGS. 1 and 2, a round knife 10 of the prior art comprises a handle 11 which is provided at the front end thereof with a rotatable protective shield 12 covering a round blade 13. The protective shield 12 is rotated to expose the round blade 13 or to shield the round blade 13.
The round knife 10 of the prior art described above is defective in design because the protective shield 12 can not be easily turned with a finger in spite of the protective shield 12 being provided in the outer side thereof with two protrusions 121 and 122 which are too small in size to stop the finger. In addition, the round blade 13 can be accidentally exposed at such time when the protective shield 12 is exerted on by an external force. In other words, the protective shield 12 of the prior art round knife 10 is a safety hazard.